fix negative indices

ssnl · ssnl · commit c2495181b48e · 2018-03-23T23:19:10.000-04:00
diff --git a/aten/src/THCUNN/linear_upsampling.h b/aten/src/THCUNN/linear_upsampling.h
@@ -17,13 +17,12 @@ template<typename Acctype>
 __device__ __forceinline__
 static Acctype linear_upsampling_compute_source_index(
                           Acctype scale, int dst_index, bool align_corners) {
-	if (dst_index == 0) {
-		return Acctype(0);
-	} else if (align_corners) {
-		return scale * dst_index;
-	} else {
-		return scale * (dst_index + Acctype(0.5)) - Acctype(0.5);
-	}
+  if (align_corners) {
+    return scale * dst_index;
+  } else {
+    Acctype src_idx = scale * (dst_index + Acctype(0.5)) - Acctype(0.5);
+    return src_idx < Acctype(0) ? Acctype(0) : src_idx;
+  }
 }
 
 
diff --git a/aten/src/THNN/generic/linear_upsampling.c b/aten/src/THNN/generic/linear_upsampling.c
@@ -14,12 +14,11 @@ static inline float THNN_(linear_upsampling_compute_scale)(
 
 static inline float THNN_(linear_upsampling_compute_source_index)(
                           float scale, int dst_index, bool align_corners) {
-  if (dst_index == 0) {
-    return 0.f;
-  } else if (align_corners) {
+  if (align_corners) {
     return scale * dst_index;
   } else {
-    return scale * (dst_index + 0.5) - 0.5;
+    float src_idx = scale * (dst_index + 0.5) - 0.5;
+    return src_idx < 0 ? 0.f : src_idx;
   }
 }
 

Original file line number	Diff line number	Diff line change
`@@ -14,12 +14,11 @@ static inline float THNN_(linear_upsampling_compute_scale)(`
`14`	`14`
`15`	`15`	`static inline float THNN_(linear_upsampling_compute_source_index)(`
`16`	`16`	`float scale, int dst_index, bool align_corners) {`
`17`		`- if (dst_index == 0) {`
`18`		`- return 0.f;`
`19`		`- } else if (align_corners) {`
	`17`	`+ if (align_corners) {`
`20`	`18`	`return scale * dst_index;`
`21`	`19`	`} else {`
`22`		`- return scale * (dst_index + 0.5) - 0.5;`
	`20`	`+ float src_idx = scale * (dst_index + 0.5) - 0.5;`
	`21`	`+ return src_idx < 0 ? 0.f : src_idx;`
`23`	`22`	`}`
`24`	`23`	`}`
`25`	`24`